Sunday, December 30, 2012

A 1:1 Balun

Whilst the cobweb is being dismantled and serviced I've put up a 20 meter inverted V dipole, just so I can use the OHR100A which is set for 20M. The dipole is completed with a 1:1 Balun.  

The ugly balun is very simple to build and does the job of removing any stray rf off the outside of the coax and away from the shack. 
It only took me a morning to make and it's from various bits and pieces I had lying around, an odd length of guttering pipe, some spare coax with an SO239 attached at the bottom of the pipe. The two wires from the dipole attach directly at the top of the balun via a choc block.


It's a bit rough and ready but as long as it does the job I'm not too bothered as it will be up 30ft and no one is going to look at the cosmetics!



The cobweb has as previously mentioned been dismantled and is now lying in the shed with the connection box drying off. Once its dry I will add some more silicone and drill some draining holes in the bottom of the box. 

The replacement fibre glass poles arrived but on closer inspection were just too thin to be used to hold the twin speaker cable, so I've found another supplier and re-ordered. 

The wooden poles are actually in not too bad a condition but I would prefer fibre glass to add strength and to make the antenna lighter. The new poles must be near to an inch in width to fit the metal sleeves and will be hollow therefore lighter.

Wednesday, December 26, 2012

Servicing the Cobweb Antenna


Finally I've got round to begin the service of the home-brew Cobweb. Taking it down from the mast wasn’t as bad as I thought, I decided to do it now as the weather forecast is not good with high winds expected over the next few days, so while there was a break in the weather I zipped up the ladder and began the removal process.


 Once down the initial inspection was that it didn’t look too bad considering it’s been up on the mast for nearly two years and been subject to some pretty bad weather conditions. A bit of rust here and there on the metal tubes that hold the wooden poles, but perhaps through luck or my building capabilities it has managed to withstand all that has been thrown at it! 



  The wooden poles and the box are covered in mildew and slightly bowed, but still sound, the cables are fairly loose which I suspect is the main reason my SWR has been out, especially on 20 meters which at the last reading was 2.5. Interestingly I thought the box would have been pretty rusty inside but surprisingly looks very clean apart from a good ½ “ of water slopping inside, first thought was hmm, I forgot to drill any draining plugs!


 The wooden poles are going to be replaced with fibreglass, I managed to find some ex army surplus which should do the job nicely but I will have to wait as I’ve only just ordered them so it will take a few days to arrive. Since the main box is in such good condition I will do little except give the outside a good scrub and more importantly drill a couple of draining holes. 


The silicon grease has done its job and kept the contacts all clean and rust free, I'm amazed there is no rust on the copper wire or the steel screws. Originally I bought a Cobweb (back in the 90s) for the grand sum of £160 and when I sold it I remember inspecting the box and seeing how badly rusted everything was, so I was expecting the home-brew to be the same, just goes to show what a bit of silicone will do to protect.


Over the next few days I will tighten the cables and recheck the SWR and if needs be replace any that are suspect, luckily I have some spare cable that I got last summer from Maplins, (our version of Radio Shack). 

Looking inside the box it is a remarkable simple system that is very easy to build and yet gives great results. This is easily the best antenna I've ever built and quite honestly if I can build one anyone can. If you want further information look at the Cobweb Revealed website or alternatively please ask and I'll be happy to help where I can (but I warn you now I don't understand the theory, hi hi). I will include as many picture as I can during the service process so you can see just how easy it is put together.

Friday, December 21, 2012

OHR100A Completed

The OHR100 A is now complete, a few QSO's later and I must admit I'm pretty impressed with this little QRP radio especially on the receive side. The Bandwidth takes a little bit of tweaking to get it just right but works well and can quite easily cut out the clutter from other nearby stations. So far I've had some good reports with stations around Europe and I have no doubt that I'll be able to contact across the pond with my 7 watts of power.



I've managed to get hold of a frequency counter off Ebay which has made a big difference, I don't have to guess where I am within the CW side of 20 meters which does speed things up a bit when searching for QRP stations. 

Inputting the IF offset frequency took a bit of thinking as I'd never done it before, but after reading and re-reading the instructions I eventually got there and had it all set up. The casing is a bit scruffy, but I'll give it a lick of black paint or some Hammerite to tidy it up a bit. I fitted an internal 9v battery and also added a small on off switch to save power when not required. It does the job nicely and I amazed how quickly I built it all up, another thing 6 months ago that I wouldn't have had a clue at doing!

I eventually gave up on the old TH-215 E and went shopping on Ebay, I managed to pick up a TH-22E for a few quid. It's an excellent little radio and works well when connected up to the Yagi, only 5 watts but that's all I really need as I'm 750 ft above sea level so can get out pretty well on low power.


The next project I must get round to (having said I was going to do it back in the Summer) is to take down the Cobweb and give it a good service. The SWR on 20 meters is up at 2.5 so I'm having to use the ATU all the time now for the RMs and the OHR. It probably just needs tightening, but I'm going to open the box and give it a good clean and re-grease the connections, after all it has been up there for a long time now. I'll take some pictures so you can see just how easy it is to build one!

I've got 10 days off over the Christmas break so I shall pick a good day weather wise and do the work! Also over the break I am going t have a good think about what to do next radio wise, another kit perhaps, or maybe an old transceiver that needs a bit of TLC? Well see what happens in 2013.

On that note May I wish you all a Merry Christmas and a Happy New Year.

Thursday, December 13, 2012

OHR100A Build Part 2 (The Chassis and Alignment)


After re-checking all the soldering and making sure there were no obvious mistakes, I started on the chassis, firstly installing the SO239 socket and then attaching the optional ten turn VFO tuning pot followed by the AF and RF gain switches and the Bandwidth and RIT switches. The wiring instructions were fairly easy and I soon had everything connected up and ready for a smoke test. 

 All ready for the smoke test

The only problem was I didn't have a 13.8v power supply! The RockMites run off batteries and the FT1000 MP V has its own separate power supply. So on to Ebay and I quickly found an old but unused power supply for the princely sum of £15.

Two days later (a miracle in postal terms) the PSU arrived and after wiring in a 1A fuse I was able to carry out a smoke test. Do you ever have that feeling of dread, fingers on the switch wondering if you really will get smoke or just nothing happens? I must have been waiting for half a minute before I pulled up enough courage to switch the transceiver on. I turned the switch and bingo, the radio came to life ....what a relief!

Once I'd got hold of a power supply it came to life!

A quick play on receive and I found some cw, turning on the FT1000 MP and matching the incoming signal I could see that I was tuned in to 14.045 with the VFO fully turned anti clockwise, so I wasn't far off, the VFO toroid just needed some tweaking which was confirmed when I attached the MFJ 259 and using the frequency counter read that I was at 23.400MHz, just off the mark as the instructions quote 23.000MHz.

 So all I had to do was alter the gaps between the windings on the VFO toroid L114 to bring the frequency down to the required 23.000MHz as per the instructions. At the same time I had to tweek the caps for maximum power output between 100mv and 400mv, but this was fairly easy using my DMM. Once happy with the toroid readings it was a case of pinching some of my XYL's clear nail polish and giving the toroid a good coating and leaving for 24hrs!

 The toroid at L114  that needed a tweak

I must admit the hardest part I have found with this kit is the alignment, I've had little experience of this process but with the help of the instructions I managed to get through but it took time. You have to have a frequency counter and a DMM for this project and to be honest I'd never used the MFJ as a FC so it was all new to me and there are no instructions in the MFJ manual about how to set it up for frequency counting. In the end I attached a short piece of coax fitted a PL259 to one end and trimmed the earth off the other end leaving just the central wire. By chance I had a very narrow metal tube that fitted over the wire giving it strength and hey presto it was an excellent probe.

 The homebrew probe attached to the MFJ

The radio is now virtually complete except for the optional LED that I have to fit. I've had a good play but I haven't attempted a QSO yet, hopefully this will be done over the weekend. It's putting out a healthy 7 watts on the dummy load, but I've reduced this to 5 for QRP. First impressions are that the receiver is excellent especially when using the bandwidth, it certainly matches up to other radios I have owned. The 10 turn pot although smooth gives you little idea where you are within the CW sector of 20 meters so I suspect I will purchase the OHR Digital Frequency counter to make life a little easier.

Overall I'm really pleased; I've come along way since the early days of the RM builds and my confidence as a QRP builder has grown dramatically. Reading the reviews on Eham, the kit is probably classed as an intermediate, so hopefully I've passed with flying colours and now can look towards building my ultimate homebrew kit, the K2 !! 

In the meantime I shall enjoy working some QSO's with my trusty new OHR100A. Once I've added the LED I will post some pictures of the completed Radio.

Sunday, December 9, 2012

OHR100A Build


Finally the OHR100A arrived but in the end I had to nip down to our local postal sorting office to collect it as they were complaining about how busy they were and it was going to take time to deliver. 

The parcel was well packed with individual sections of the kit separately kept apart which made things easy for identification. Marshal certainly makes sure of doing a good job in packaging as everything is nice and secure.



So the build of the OHR100A begins. To start with I thoroughly checked the inventory to make sure I had everything; I ticked off each part as I went and seemed to be all there so I could get on and make a start. I don’t plan to rush it; I’m going to take my time and build in roughly 2 hour slots so that I don’t over do it and make silly mistakes. The first part is to install several diodes and the IC sockets making sure that all are correctly positioned on to the PCB board before soldering.



The instructions seem very clear, certainly as good as the Wonderlabs notes which helps greatly when a newbie like me is attempting something a little more difficult than the RockMites. Amongst the instructions is an overlay sheet with clear diagram of where each part should sit which is very useful.



6 hours later and I’ve installed the diodes, chips, chokes, resistors, trim caps and capacitors, the only problems so far have been a slight issue with soldering as I’m having to re-apply a small amount on a few components to the top of the PCB board as the soldering is occasionally not penetrating through the holes, this is more likely because of the solder I’m using but in actual fact probably helps in double checking that everything is soldered correctly.


Approximately 9 hours later and I've all but completed the PCB board. Just the IC's to slot in to place and add in the Molex connectors. The toroids were a little fiddly but I think that is probably due to lack of practice and experience, but once I had done the first the others seemed to wind OK. 

Interestingly in the picture below you can see my one mistake that I had to rectify, which was placing the transistor D105 in to U104. As soon as I done it I realised my mistake but then had the job of carefully removing the transistor and then soldering it in its correct position. The one thing I've learned is that as soon as you feel at all tired take a break because that's when mistakes are made!


Now I have to assemble the chassis with all its components which hopefully won't take too long and then just wire up and do the smoke test.......More to follow!

Sunday, November 25, 2012

Good News With the OHR100A

Well as soon as I started to worry that the OHR100A was lost forever in the vacuum of the postal ether I get a note from the Royal Mail telling me they have a package for me, but the bad news is I have to pay the sum of £35.50 for Customs and RM handling charges! £8 for handling charges, crazy! Anyway at least it's arrived and I know that soon I will  be once more happily getting stuck in to another building project.

The TH215-E has definitely shorted I found that the fuses J1,2,3 and 4 have all blown so something has caused it to fail. To be quite honest unless its a simple fix like an audio amp replacement I may just give up and buy myself another 2 meter rig off Ebay, we'll see.

Friday, November 23, 2012

Lost OHR 100A and TH-215E Problems

Still no sign of the OHR100A! I contacted Marshall at Oak Hills Research and he advised me to wait another week, before approaching USPS, but I have to admit I’m beginning to worry, I have ordered a few items from the US and they haven’t taken this long.
My only hope is that the package is stuck in the UK customs and it will hopefully arrive in the next couple of days. Looking on the USPS website Marshall kindly gave me a tracking number but all I see it that it was last seen in Jamaica NY on the 04/11, after that there’s no further information. It’s typical you build yourself up ready for your next project and then it doesn’t arrive!
Whilst waiting for the OHR100A I’ve been trying to figure out what is wrong with my old 2M TH-215E handheld. It switches on fine and even transmits ok but there is no sound coming from the speaker.
Using the MMD I’m getting output from the speaker and if I hold it close to my ear I can just make out the squelch, so I think it’s more likely it is the pot playing up. I’ve dismantled the radio and have attempted to give the pot a really good clean with some switch cleaning lubricant.

 The disassembled radio, on initial inspection all looks ok.

I’ve checked the PCB and can find no cracks or any sort of damage so at the moment I’m slightly at a loss as to where to progress from there. 

I've given the pots a really good clean but they are sealed units which does not help, so it's a case of gently feeding in the lubricant and turning the pot back and forth.

The speaker looks ok and I've checked the connections with the MMD and am getting output.

I suppose the options are that I make sure the extension speaker plug is not cancelling out the internal speaker, check all the traces to the speaker and last case scenario try and find another pot and replace the old one. ................Anyone had a similar problem let me know!

Friday, November 9, 2012

Audio Amplifier Kit


Still waiting for the Oak Hills Research 20 meter kit to arrive although strangely the LED kit turned up the other day, but nothing else. 

So I’ve been tidying up the shack and getting all my soldering irons cleaned up in readiness for the big day. I also purchased an audio amp kit this time with a bit more power 7 watts, my home brew audio amp is fine but lacks oomph. The new amp works well with the RMs and just means I can listen out to who is around when out of the shack in my other workshop.


I've also had ago at installing the CW filter I bought from Hamshops, and although it works  I don't think I've set it up correctly. when I add a 9v battery there is no change in sound so the small amp doesn't seem to be working. Without the battery the filter continues to work but all received signals are just quieter and there doesn't seem to be any filtering. I suspect when I originally built the filter I messed up the soldering of the amplifier hence its not working, however I will carry out further tests and see if I can find out the problem.

All three RockMites are now safely in the shack and used most days when I have the chance to play radio. I've had some good contacts especially with the 20 meter RM where I've gone over 1k miles which I'm pretty pleased about. The 30 and 40 get good contacts with Europe and the average distance is around 500 miles which is nothing to be sniffed at.


In fact the shack is looking pretty good a the moment and I'm amazed how it slowly filled up with various bits of kit. So I had a bit of a spring clean and re-organised things especially as I know I'm going to have to find room for the extra OHR 100A. In my haste to clean up I dropped my old Trio 2 meter handheld, it still switches on but there is no sound I've checked the speaker connections and they are all working so I suspect it's something a little more serious, never mind it will keep me occupied during those winter months, or it's an excuse to go out and buy myself a new one!




Do you like my old Royal Enfield in the top right corner?

Tuesday, October 30, 2012

Another QRP Kit

Well I’ve gone an ordered another kit, this time it’s the Oak Hills Research OHR100A
I suppose once I’d seen it I knew it was the next sensible step up from the RockMites, I’ve chosen the 20 meter version, I did think about the 30 meter but quite honestly the last RM I built was for 30 meters and its working so well that I really don't need another rig for that particular band at the moment.
This rig has a bit more power 5 watts, so I should get a lot more first time contacts, thats the one thing about RMs, you have to be patient when calling CQ!
I'm really looking forward to it's arrival I think I'm definitely addicted to QRP building and this should be fun. Not sure how long it takes to dispatch but also I will need to take into consideration all the problems that hurricane Sandy may bring so I need to be patient.
I’ve also ordered the extra 10 turn VFO tuning pot and the LED kit, I thought I might as well get everything straight away.

This build will really be the prototype for the main event the K2, so I hope I find it fairly straight forward in construction and also put in to practise all that I have learned when building the RockMites.
Providing all goes well I will add photos and descriptions as I go along, might prove interesting for some budding home builders. If it’s all successful then I will certainly start looking at the K2 but I doubt I will get that until sometime next year.

Wednesday, October 17, 2012

The Higher Bands Open Up

I have just been skimming across the bands and this morning 28MHz is wide open, I’ve heard VKs VUs and ZLs and it’s a refreshing change to the normal quiet hiss of the band!
Interestingly there never seem to be any slow operators in the early morning, whenever I switch on first thing you always hear the diehard Dxers tapping away, mostly at speeds that I find difficult to keep up with.
Always first thing in the morning when I fire up I'm too keen and I have the typical CW operator’s problem I find I can send faster than I can receive. I call it BNC (Brain Not Correlated).
Sometimes when I hear a distant station and dive in giving a quick reply they come back at me like a machine gun because I’ve gone in at such a quick speed.  I then have to put my brain in to gear and concentrate very hard to translate the reply.
If it’s a standard reply such as “gm es tnx fer ur call ur rst 599 etc”, then I’m ok but if the conversation alters then I really need to buckle down and think! Its classic mistake that operators can make, but it’s not the end of the world, after all it’s your hobby so enjoy the challenge and it's a great way to speed up your code!
I’m still at a loss at what kit to build next, I’ve been looking at my ultimate build, the Elecraft K2, I just love that transceiver and a real challenge to build, but like all things it comes at a price which is something I just cannot afford at the moment, but one day I am going to buy it, it’s just a matter of time.
I’d also love to have the K3 the ultimate CW operators rig, but its a lot more money (nearly £2k) and I already have my super rig, the FT1000 MkV which is a very good radio. So if I ever did buy the K3 the MkV would certainly have to go to part finance the K3, which I'm not sure I could do.
In the meantime while I dream for my super kits I now want something to fill the gap of the RMs, basically it must be a challenge above the build of RockMites so more than likely its going to be a Hendricks or Oak Hills Research kit.
It must be a minimum of 5 watts with CW only and definitely have a VFO as I’m not too keen on being limited to a small section of the chosen bands.
Certainly with the RockMites it can be a pain when you switch on and the band is swamped within your particular frequency, you have little or no ability to move away. I know you can mod the RockMites but I feel I want to keep them as they are and move on to something new.
In the meantime I’ll carry on tapping away at the key especially whilst the higher bands are open.

Thursday, October 11, 2012

A Simple Manual Antenna/Radio Switch

Now that I have three RockMites and one FT 1000MPV to play with I wanted to make it easier to switch from each radio, the simple solution was a basic antenna/radio switch.  
I had an old 3 way Altai switch from years ago but quite honestly it was a cheap bit of kit and anything above 50 watts it would probably burn out. So I decided to build my own using various bits of junk I had in the shack.  
I pinched the four SO239s from the Altai which were fine but interestingly on further inspection the Altai was definitely on its last legs, the plastic switches on it were virtually worn away. After rummaging further in the shack I managed to find another SO239 to make 5 connectors in all.
I also had a small aluminium/aluminum enclosure which would do nicely for the case and being metal would take care of the groundings and any stray RFI. I found a one pot 4 way rotary switch, but it was plastic job, fine for a guitar or something similar but I doubt would have lasted very long for what I wanted.
So I decided to buy something heavy duty and after trawling around the web I found a UK company that sold 1960s rotary switches and I spotted a good solid 1 pot 4 way switch that would be just the job.


It cost me £6 but when it arrived I knew I’d bought the right switch, it was a good solid bit of kit, nice and heavy with a break before make connection.
I soldered some 14 gauge wire to the SO239s and fitted them to the enclosure, after cleaning up the switch I drilled another 16mm hole in the top of the enclosure and fitted it in to place. 

Finally I connected up all the 14 gauge wire from the SO239s to the switch and gave it a smoke test. The SWR was good on all five connections and another useful bit of kit was completed. 


The nicely thing now is that I'm not chopping and changing antenna connections to different radios all the time, with a simple twist and satisfying "clunk" of the heavy duty switch I can connect to each radio with ease.

Sunday, October 7, 2012

Oner Stockton Wattmeter


To get an idea of QRP power and SWR for the RockMites I bought the "Oner" Stockton Wattmeter from Kanga Products

It comes in kit form and is a simple circuit and fairly easy to put together. I suspect many QRPers will know of it and what a useful bit of kit it can be. It only took me half a day to put together and now at least I have a more accurate means of measurement. 

I had an old enclosure that was able to use to fit the kit, the hole for the meter was a bit too large, but a bit of tape fixed the problem otherwise all the other connectors and parts fitted in nicely!

  
I'm at a bit of a loss now, no more RockMites to build and although I'm having fun operating them I need some kits to build, I've obviously become an addict! I think I've said before I've got my eye on the 5 watt CW kit from Oak Hills Research or possibly the similar CW kit from Hendricks.
We'll just have to wait and see and to be more precise what I can afford!

Thursday, October 4, 2012

RockMite 30 Update

Well some good news, I’ve had my first QSO with the RM30 but there have been some minor issues along the way.  
After completing the build and doing some further testing  it became obvious that the transmit was not working as it should, I was using the 2N3053 transistor with the 2 ohm resistor in R18 and of course the bifilar toroid filter mod in L1, but I was only getting about 400Mw out when I should have been getting around 700Mw.
On further investigation/checking and through chatting on the Yahoo Rock-mite forum it eventually came apparent that I was using the wrong toroid FT37-6 as opposed to T37-43.
 Unfortunately I did not have that particular toroid so after having a good think realised the best way forward was to revert back to legacy and remove the T37-6 and pop L1 back in and use some jumps to bypass the trace cuttings.
Actually surprisingly enough it did not prove too difficult and I soon had the RM back up and running pushing out approximately 600Mw of juice.
At the same time I had a play with various transistors I have, the standard 2N2222 and the 2N3053 plus another, the 2SC799 which in theory can give you up to 2 watts of power. Sadly with my RM30 it hardly gave me any power, so either it’s broken or my set up is incorrect for that transistor.
So I reverted back to the 2N2222 and after a couple of attempts Calling CQ this morning I got DL6FAX, Konrad in Korbach a distance of 670 miles , not bad for my first attempt and Konrad was kind enough to give me a 569!
I’ve now ordered the correct toroid which should arrive later this week and then I will do some further experiments and we’ll see how we go from there.
The main thing is all my RM’s are now built and thankfully working correctly, something I would not have dreamed of if you had told me at the beginning of the year. 

Some further news regarding batteries, at present I have been using standard 9v batteries, which are fine but obviously not rechargeable. A member of the Yahoo RockMite forum announced last week that he had purchased a re-chargeable 12v battery from China which by all accounts seemed to fit the bill for RockMites really well.


So I took the risk and also bought one, it arrived the other day and I’m really pleased with it. It comes complete with charger and 3 pin plug (for UK users) and seems to hold the charge pretty well. It’s excellent for when I want to get out and about, not bad for £8.00!

Sunday, September 30, 2012

RockMite 30 Arrives and the Build Begins

The 30 meter RockMite kit finally arrived in the post and this weekend I will begin the build and then complete my RockMite trilogy!
The intention is to incorporate all the mods I have used on the 40 and 20 RMs, adding the more powerful 2N3053 transistor, reducing the resistor R18 to a lower value and altering the zener diode D5. I will also soften the sidetone with Dave Benson's recommendation of a "10 10" filter (10 ohm resistor and 10uf capacitor)
Then on top of that I will add the bifilar PA mod (toroid) and include the CW audio filter I built earlier. Add sockets to the components I may want to change, which will include the crystals as the frequency I will be using is 10.116 instead of 10.106, (I’ve done some research here and 116 looks a little friendlier for my slower CW)! I managed to pick these up from the same company who sold me the audio filter, the Hamshop. It's a good shop for buying those sort of parts that are sometimes hard to come by.
Finally I’m changing the enclosure to an aluminium case which will be slightly bigger to take the audio filter and also so should I wish add extra components in and outside the case such as LEDs switches etc. So, in all I should have a nice little RM transceiver complete with all the mods and an output of around 700 milliwatts.
I’m also very tempted since 30 meters is my favourite band, to purchase the small amplifier from QRP project a German company that has some very good reviews. Getting the power up to approx 10 watts just for the one transceiver might prove fun especially on 30 meters.  
The other project I’d like to go ahead with is to buy the OHR 100A 5 watt CW transceiver from Oak Hills Research. I’ve been eying this little kit up for some time and believe it will be ideal for me to progress in my QRP kit building quest but we’ll wait and see how I am after the completion of the final RockMite build. 

So on with the build:
The first procedure for the RM30 mods is to cut some of the traces between various components, I thought I would do this first while the PCB is free spaced giving me more room to work.


So my first trace cut was for the sidetone filter which was between pin 5 on U3 and C8 which you can see top right. The next cut was for the PA toroid mod which again on the bottom of the PCB is a cut between L1 and C14 (middle left of the PCB) a bit tricky as it's fairly close together.


Turning over to the top of the PCB and continuing the trace cuts for the PA mod I cut a gap at both ends of the trace between L1 and C1 (middle right, a bit small but the picture will enlarge).

With all trace cuts completed I will now start fitting some components and sockets. I will also fit the PA mod toroid by inserting the jumper lead between C1 to the junction of C14 C15 and L2 and solder up the centre tap of the toroid (ab) in to L1 and then a and b taps in to the holes either side. Below is the details of the toroid fairly simple but a first for me!


Two hours later and the majority of the PCB build is complete with the toroid in place, which was a little fiddly to fit but I finally got there in the end. All I have to do now is insert the sockets and add the 2N3053 transistor together with the lower value R18 and the 10.116 crystals. Finally to finish off before the smoke test add the "10 10" filter on to the bottom of the PCB.


I'm pretty pleased so far, my soldering has certainly improved since first starting a few months back on the old RM40, just proves practice makes perfect! 


 The "10 10" filter for the sidetone mod and the jumper to complete the PA toroid mod.


Nearly there, the completed RM slotted in to the enclosure case, you'll note there is plenty of space left as I want to add the CW filter and internal batteries. I've also added an LED and an off on switch just to make things easier.

 The internals look fairly neat for even to me! I've fitted sockets to the transistor (which is not in the picture), and for the crystals, hence the copper ring which acts as ground and can be opened up when I want to replace each crystal.



And finally all sealed up in the lovely new enclosure! I will add some small black decals so that I remember what everything does. So far no successful QSO but to be honest I haven't really given it a proper try, although my Brother-in-Law down the road, (about 4 miles away) could hear me testing when he was listening out on his FT1000D, so I am getting out at approx 700Mw, I will attempt a proper try later this week, so hopefully the next post will bring some good news!

Thursday, September 20, 2012

Audio Filter SMD Update


I’ll take it all back re Surface Mounts Devices; They are fiddly little things and I was cursing and swearing away as I attempted to solder the individual parts on my audio filter! I had no problems with the SMD on the RockMites but when doing something as small as the audio filter it is a different game.
Everything within the audio filter is so small it takes a lot of getting used to and lessons have  been quickly learnt. Perhaps I shouldn't have started with such small resistors and capacitors, but hey, you have to start somewhere......... Here's a few tips I learn't along the way:
1. Get my eyesight sorted; wearing two pairs of glasses over each other does not work, go out and buy a headband magnifying tool or a large magnifying glass on a stand!
2. Have a clamp which will hold the small circuit board, otherwise the thing moves all over the place as you attempt to solder tiny fiddly resistors and capacitors. (Re resistors and capacitors it's a good idea to work out the value beforehand hence the magnifying gear......he he)!
3. Don’t use the XYL’s old pair of tweezers, believe me, they don’t work and she wont appreciate it either; get yourself a good pair from the local hardware shop.
4. Have the correctly tipped soldering Iron and the right solder specifically for SMD work; Try soldering with a chisel end? (It doesn't work, I know), you will find that soldering SMD’s is much easier with the right tools.
5. Give yourself plenty of patience especially if you are new to this lark; believe me it took me a while to actually get something soldered on to the board. After numerous attempts I finally got something in the right place but at one stage I was doing more un-soldering than soldering. 

 The circuit board although small looks like it's been in a war, (R5 looks a bit off!) whether it will work is another matter, I will at some point put the multi meter on it but at the moment I reckon I still need to calm down!  
Other news; I'm still waiting for the RM 30 which is sadly still stuck at Wonderlabs awaiting spare parts. No matter, like soldering SMD's, patience is the order of the day.

Monday, September 17, 2012

Building a 2 Meter Yagi

I managed to purchase a Kenwood TH-215 2 meter handheld off EBay for the princely sum of £11.50. 
The radio works ok off the mains but the two batteries are not holding their charge, no real surprise as the handheld is an old bit of kit. So I'm on the lookout now for a spare battery, whether I find one could prove interesting. I rarely use 2 meters but to be honest there is a good morning net that I'm missing out on, plus I can keep in touch with all the local operators.

Anyway now that I have the rig I needed an antenna and although somewhere in my shed I have an old 2m vertical I quite fancied the idea of building a Yagi. Nothing too elaborate just a small 3 element to boost things up. So I had a search on the web and found details of a fairly simple yagi build  which seemed to promote a good db gain.
According to the details the maximum forward gain was around 8db (6 dbd) on 145 Mhz. So doing the math, with 6 db (6 dbd = 8,15 dbi) gain, this antenna offering an “effective radiation power” 4 times greater of the transceiver output (without Coaxial-Loss), i.e with my little handheld with an output power of 5 watts, my ERP will be multiplied 4 times = 20 Watts (in the forward gain). 
 
Reading further it went on to say this antenna was compact enough (78 cm boom between Reflector-director) with excellent F/B ratio (20 db). The Impedance on center frequency (145,000 MHZ) is 65 Ohms, so in practice the antenna needs a "matching system" for a 50 Ohms coax and to get the SWR down to 1:1, the website recommended a "Hairpin" system which is very simple and effective "matching method"

 
So I gave it ago and had a prototype antenna built within a day, but without the hairpin method and some slight alterations in measurements which proved costly as my SWR was totally out. 

Build number two I followed the plans regarding the measurements and managed to find some thick copper wire for the hairpin. After checking everything was tight and correct I did a check with the MFJ 259 and Bingo I had an SWR of 1:1 at 145 Mhz. Just goes to show, follow the plans and you can’t go wrong!


Build Number two, it's pretty basic, held together with pressure clips and tape. The elements are made from the old aluminium tubes I had on the Moxon and the boom is an old TV boom I found in a skip.


The Hairpin fitted in place and taped up to make it weather proof, luckily I had some reasonably sized copper wire which I had originally used when constructing the Cobweb. Again fairly basic but as long as it does the job.


The final product slotted in to the rotator and mounted on a 20 ft scaffold pole. Its just enough height to clear the nearby tree and first impressions look good with a 1:1 swr at 145.00. I have already heard some chatter from pointing north up the Severn valley towards Birmingham and this morning before going to work heard the local Cheltenham net having a chat. Certainly when rotating the signal fades in and out so all seems to be working ok. Just got to do a transmit to make sure I'm getting out!

Monday, September 10, 2012

CW Audio Filter and Audio Amplifier

The CW filter from Hamshops arrived in the post today and as I have this week off I hope to get it built and set up with the 30 meter RockMite as soon as I can, although the RM 30 is still to arrive. The first thing you notice with the filter is just how small it is, believe me it's tiny and of course its surface mount! After watching a few demonstrations on You Tube I'm pretty certain I shouldn't have an issue when it come to SMD assembly.


I added the 5 pence coin so you get a rough idea of the size, apologies for the quality of the picture but the camera has literally just come to us and I'm still getting the hang of using it!

Good news on the Audio Amplifier front, I completed the build and it's working nicely. I'm especially pleased because it's my first home brew PCB build and although a very simple circuit it took some time to work out the layout, but once you have that sorted and know the basics like where ground and live are going to end up it all falls in to place! Its just a simple circuit using an LM386 amp, I added a few extras like the switch and LED, all good practice.


Fingers crossed the RM 30 will arrive in the next day or two and I can then get on to complete the collection of RockMites. Already thinking what an earth am I going to do when it's all completed, but I have joined the GQRP club and hope to gain some ideas about some more projects.

Tuesday, September 4, 2012

Good Conditions and More Projects

The bands were wide open over the weekend and I managed to take advantage and get some good qso’s, the highlight being on 28 MHz with Carlos in Sau Paulo who gave me a 579 not bad for a distance of 5816 miles. Admittedly I was using 250 watts but for me 28 Mhz is not brilliant on the old Cobweb.

When I had the Moxon up I could contact stations with ease on 10 meters but for some reason the Cobweb doesn’t like it too much. I constantly check the swr which is good at 1:2:1 but it just seems foggy if you know what I mean.
I’m still awaiting the arrival of the 30 meter RockMite which hopefully will turn up sometime this week. I now have all the extras I require, the 2N3053 transistor, the reduced value R18 and I have wound the toroid choke so it's all ready for the kit. Also I 've ordered a small audio filter kit from Ham Shop CZ which should be arriving any day. Together with the RM 30 the PCBs should both fit snugly in to a nice metal enclosure I've bought from the local Maplins store.
In the meantime I’ve decided to redesign my audio amplifier project, before it was literally an LM 386 with a 5v regulator with no resistors or capacitors, hard to believe I know, but I did some more research and have found some better schematics which I am going to have a play with because I'm sure I can do a lot better.
I’ve bought various capacitors and resistors as well as a 10k potentiometer, also some stripboard but after examining it I suddenly realised how on earth do you use it?
Normally with all kits the circuit board is printed, I have no experience of how you solder components on to a stripboard, so I went back to the net and had a read on how to place components and use a track board cutter.
It looks like fun but I can see it isn’t going to be easy to start, but there are plenty of examples of audio amps with schematics and stripboards designs. So as soon as I get the chance I will have some experimentation.

Wednesday, August 29, 2012

Toroids and an Audio Amp for the RockMite

I’m still awaiting the arrival of the 30 meter RockMite, but its early days yet and normally takes around a week to ten days to arrive.
I plan to add all the mods I’ve done for the 40 and 20 but also have a play at changing L1 for a toroid. I’ve taken the details off the RockMite forum and its look pretty easy to do, but as I’ve never done any windings before I’m a little nervous; there are many claims from hams that winding a toroid can be a painful experience!
Well I gave it a quick go last night and in all honesty I didn’t seem to have a problem, I had to do 7 bifilar turns on a T37 core, it was just a matter of making sure that the enamel copper wire didn’t twist and obviously had the correct number of turns and the connections were correctly linked together.
You’ll notice I describe all this in a distinctively non-technical manner. I must admit I’m not really a technical person and my electrical capabilities are fairly basic, but I do believe that by reading up and asking questions you can learn so much, this by the way does not just apply to electronics but everything. My motto is never be afraid to ask even if you think its the most dumb question, someone will know the answer!
My electronic knowledge is as I said basic, but I passed the amateur radio exams and I understand enough to get by. I still get confused by schematics, I know all the components but I make the common mistake of not separating the drawing from how it will actually be laid out on the circuit board and also I get confused with ground and wonder why the ground connections are not shown connecting to “something”.
But I’ll persevere and no doubt eventually in a few years’ time when I read back on this post I will wonder what all the fuss was! I look at all these RockMite projects as a bit of fun but also a big learning curve. In the near future there is no doubt I will buy a larger transceiver project, I don’t want to purchase an expensive kit radio and then halfway through find out I’m stuck, I want to be able to build it and be confident in understanding how it works.
The other project I’m attempting is a simple audio amp using an LM 386 chip. I found a You Tube instructional video and decided to give it a go. My first attempt ended in failure because the chip I was using (pinched out of an old Lake morse oscillator) had failed and when I had completed all the wiring and gave it a test I could hear sounds but they were not amplified.
I rechecked the entire wiring etc. and came to the conclusion that the chip was definitely faulty. So at the moment I am awaiting another chip which hopefully will arrive in the next day or two.
Unfortunately I never got round to servicing the cobweb, bad weather and other jobs got in the way, but I have some holiday coming up and I will finally get round to giving it a good clean.

Thursday, August 23, 2012

Cleaning the Cobweb and Playing with the RM's

I’ve still not got round to taking the Cobweb down for its annual service, I guess I’ve been too busy building all the RockMites, but hopefully as this weekend is a UK bank Holiday I shall climb the ladder and remove the Cobweb from the mast and give it a good checking over.
I suspect the wire contacts within the main junction box will need a good clean and probably re-water proofing, also I need to recheck the SWR on some the bands especially on 20 meters as the wire has drooped and stretched from last winter’s gales and the odd bird perching on the antenna.
For a home brew antenna it’s pretty rugged and it does take a beating especially in the winter storms. As it’s been up for two years now without me tinkering it really does need to be just checked over. Hopefully it will require little work and I'm counting on the old adage “if it ain’t broke don’t fix it”!
 I’ve been looking at replacing the inductor L1 in both RockMites with a simple toroid mod which evidently improves power and stability, I’ve never wound a toroid so it’s a first for me, but I need to learn this skill especially if I am going to be buying more kits which will certainly have toroids!
Since my success with the RM20 I have replaced the 2N2222A transistor in the RM40 with the more powerful 2N3053 and also switched R18 to a lower value. Also like the RM20 I soldered in some sockets so that I could swap out components if required. This minor mod should change the power output on the RM40 to approximately a watt. 
I've yet to test though as I thought this wouldn’t take me very long but once the mod had been completed there was silence when I fired up the rig. After much muttering and investigating I traced the problem back to R5 a simple case of one of the potentiometer wires coming loose. which I will resolder as soon as I get the chance.
Finally I've decided to complete the RM collection by purchasing the RockMite 30; well readers must have realised by now, I'm hooked!

Monday, August 20, 2012

First QSO with the RM 20

Just completed my first QSO with the 20 meter Rockmite.

After returning home from work I decided to fire up the RM 20 to see what was about. The band was pretty quiet so I prepared myself for a CQ call when all of a sudden a station came up right bang on the frequency calling CQ.

I quickly replied with my callsign and Erkki, OH7QR came back immediately and gave me a nice 579 report with some QSB.

Well it took a while but the conditions were not brilliant over the weekend, lots of noise, so I've had to wait patiently and just bide my time for the band to quieten down.

I'm pleased as punch, a distance of 1346 miles with power roughly at 800mw on a 9v battery.

I love this QRP stuff!

Thursday, August 16, 2012

Rock-Mite 20 Completed

The new 2N3053 transistor complete with heat sink and the pack of 2.2 ohm resistors arrived so last night I managed to complete the build of the RM-20.

The smoke test worked with no problems and I was soon listening on 20 meters to see what was about. I hooked up the RM to a dummy load and gave a tap on the key, all seemed to be working OK and I was keen to see what output I was getting with the new transistor upgrade.

First impressions look like about 800mw with my 9v battery so hopefully with a 12v power supply I may well get over a watt.

I also changed the zener diode on D5 as suggested by Colin M0CGH to give a wider RX/TX at around 700Hz.


With the upgrade of the transistor I installed some sockets in to the PCB so that if need be I can chop and change transistor/resistor value to see what matches best for getting maximum output.

The sockets also raise up the transistor (which is considerably larger than the original 2N2222A) above the surrounding bits and bods so that I can fit the heat sink and it doesn't get in the way of anything else.
The heat sink maybe be a bit over the top but the enclosure is quite large so there is no issue when fitting.

Can't wait now to have my first QSO, although I'll doubt I'll beat Colin's distance who emailed me to say he had got the States on one of his first calls, a small distance of some 3000 miles!

Saturday, August 11, 2012

RM-20 Build Gets Started

I managed to start the build for the RM20 yesterday and so far I have soldered the Surface mount chip and added the resistors and all the Capacitors. Just the Crystals and diodes to go and finally all the controls.

I've left out R5 as I have the volume pot and also R18 which is a 10 ohm resistor as I'm going to replace the final transistor 2N2222 and therefore reduce the value of R18 but I'll put in sockets so that I can adjust the value.


It's looking good so far, a much cleaner attempt than when I was making the RM-40 but I guess that's to be expected as you get better with practice. I was hoping to have it completed by the end of the weekend, but since I'm upgrading I will need to wait for the spare parts so it looks like it will be completed mid week.

Some good news on the RM-40, I managed to have a QSO with an MI station in Northern Ireland some 250 miles away. Mick in Armagh gave me a 449 which in the circumstances was not bad and we had a good QSO. I'll try and break that distance record this weekend!

Friday, August 10, 2012

Rock-Mite 20 Arrival


The Rock-Mite 20 arrived this week and I’m hoping to have it built over the weekend. I’ve got myself in to the habit of checking everything by lining all the parts up in an old foam pad before I start the build. 

So far everything is there so I can go ahead and start soldering U1 the only Surface mount piece, this is probably the trickiest bit to get right, but if you take your time and solder with care you should be OK.

I’ve also taken Colin M0CGH advice from the Yahoo RM forum about replace the D5 diode 4v7 with a 5v1 zener which should give RX/TX shift of around 700Hz instead of the 400Hz from the 4v7. 

Do you like the anti-static mat? This is an old disc Record mat that I've had for years and never actually placed on the record player, I knew it would come in handy one day!

The parts laid out for checking

Further updates to follow and hopefully some more pictures as the build progresses.